1. Field of the Invention
The present invention is generally in the field of electronic circuits and systems. More specifically, the present invention is in the field of communications circuits and systems.
2. Background Art
Transceivers are typically used in communications systems to support transmission and reception of communication signals through a common antenna, for example, at radio frequency (RF) in a cellular telephone or other mobile communication device. Because a receiver implemented in a communications transceiver is typically coupled to the transceiver antenna, the receiver is susceptible to damage or interference caused by an electrostatic discharge (ESD) event. In a conventional receiver, ESD protection is normally provided by a dedicated ESD transistor, such as a field-effect transistor (FET) in which the source, gate, and body terminals are grounded. The presence of a large voltage at the drain terminal of the ESD transistor, indicating the occurrence of an ESD event, can force the ESD transistor into a conductive state so as to shunt the disruptive ESD current relatively harmlessly to ground.
Advances in technology have rendered multi-band receivers more common. For example, more modern receiver chips may support multiple higher frequency receive bands as well as multiple lower frequency receive bands, where each separate band requires a corresponding dedicated low-noise amplifier (LNA) to be connected to external off-chip RF filtering. Multi-band receiver functionality requires a mechanism for band selection, as well as substantial isolation among the respective high and low bands, in addition to ESD protection for each receive band. However, conventional multi-band receiver designs typically lack a coherent approach to addressing the technical challenges posed by ESD events, band selection, and band isolation, often relying instead on an ad hoc approach implementing largely independent solutions to each problem.
Thus, there is a need to overcome the drawbacks and deficiencies in the art by providing a solution capable of selectably isolating transceiver circuit inputs and of concurrently providing ESD protection for the circuit.